Apparatus for controlling internal temperatures of foods while cooking same



Aprll 14, 1953 R. B. BASHAM 2,635,137

APPARATUS FOR CONTROLLING INTERNAL TEMPERATURES 0F FOODS WHILE COOKING SAME Filed D60. 26, 1951 2 SHEETS-SHEET l RAYMOND B. BASHAM ATTORNEY April 1953 R. B. BASHAM APPARATUS FOR CONTROLLING INTERNAL TEMPERATURE OF FOODS WHILE COOKING SAME Filed D86. 26, 1951 2 SHEETS-SHEET 2 THERMOMETERS RAYMOND B. BASHAM INVENTOR.

Patented Apr. 14, 1953 APPARATUS FOR CONTROLLING INTERNAL TEMPERATURES F FOODS WHILE COOK- ING SAME Raymond B. Basham, Fort Worth, Tex., assignor to Westronics, Inc., Fort Worth, Tex., a corporation of Texas Application December 26, 1951, Serial No. 263,351

This invention relates to temperature indicating and control apparatus for processing food. Particularly, the invention has device for cooking meat.

An object of the invention is to accurately indicate the internal temperature of meat during smoking or curing operations.

Another object of the invention is to control and maintain a constant temperature in meat being processed after the desired maximum temperature therein has been reached.

Another object of the invention is to provide an alarm, both visual and audible, for indicating the desired internal temperature of the meat being cooked.

Another object of the invention is to provide an electrical probe for a meat curing control device wherein the lengths of the electrical leads do not ail'ect the accuracy of the temperature by reference to the following description and the accompanying drawings, wherein:

Figure 1 is a perspective view of an exemplary form of meat temperature control and temperature indicating device embodying the features of the invention. v

Figure 2 is a broken longitudinal sectional view of a probe forming a part of the invention.

Figure 3 is a schematic diagram of a preferred circuit forming a part of the invention.

Figure 4 is an internal wiring diagram of the meter shown in Figure 3.

The exemplary form of the invention shown includes a box-like housing 1!) having a contact making meter ll mounted in panel I2. The typeof meter shown includes a manually adjustable pointer contact 53 for co-action with the electrically movable pointer M for controlling the hereinafter described circuit. Neon lights [5 and I5, forming a part of the circuit, are also mounted on the panel I 2.

A feature of the invention has to do with a novel probe thermometer H, which may be used singly or in multiples, for contacting the center of the meat to be cured or cooked, and which reference to a 3 Claims. (01. 175-320) probe includes a tube 28, a tapered point or tip IQ of heat conducting material mounted in one end thereof, a negative co-efiicient resistor element within the tube and arranged against the inner surface of the tip, together with an insulated lead 21 extending from said element outwardly through the end of the tube opposite said tip. Contact is maintained between the element 20 and the tip l9 by means of a slidable sleeve 22 of insulating material within the tube 18, a stationary sleeve 23 also within said tube, and a compression spring 24 between the opposing ends of said sleeves. The rearward end of the tube [8 is provided with a tubular handle 25, together with a dual conductor cable '26 for electrically connecting the lead 2| and the tube I8 with a plug 21 which, in turn, is inserted inv a receptacle 28 in the housing It. A toggle switch 29 for turning the power source onand oil, and a selector switch 30 for selecting the probe thermometer I! to be indicated. by the meter H are also shown in Figure 1 and will hereinafter referred to.

The electrical circuit shown in Figure 3 includes an electrical bridge, the four arms of which are comprised of fixed resistors 3!, 32 and 33, and one of the temperature sensitive resistors 20, previously referred to as a part of the probe 11. An adjustable potentiometer '34 is connected between two of the resistors 32 and 33, thus providing a means for balancing the bridge with a value corresponding with the minimum temperature resistance of the temperature sensitive element 26 of which temperature is'to be indicated on the meter II. The terminals between the four arms 3!, 32, 33 and 2!] of the bridge are indicated by the numerals 35, 36, 31- and 38, respectively.

The bridge is supplied with direct current by means of a transformer 39 which is connected with an alternating current source, and the leads 4!) and 4f therefrom are connected with two of the opposing terminals 3 and 3? which are located on opposite ends of the fixed resistors 32 and 33 having the potentiometer 34 therebetween. One of the leads is provided with a rectifier J2 and three fixed resistors 43, M, together with a variable resistor 45, all of which are connected in series between the transformer 39 and the referred to contract 31 in the order named. A condenser 41 is connected in parallel with the two leads i0 and M between the rectifier 42 and the first of the last referred to fixed resistors 43. Voltage regulators 48 and 49 are also connected in parallel with the leads 49 and 4| between the three iixed resistors 43, 44 and 45. The first referred to voltage regulator 48 has a greater voltage drop than the last referred to voltage regulator 49, and whereby a more constant voltage regulation is provided. As will become apparent from the description of operation, the voltage supplied to the bridge must be stable and well below the maximum error tolerable in the final measurement at the meter II. H

As shown in Figure 3, the thermometer elements 26 are selectively connected with the terminals 3! and 38 of the bridge by leads 50 and 5|. Corresponding sides of the thermometer elements 20 are all connected with a single terminal 52, in the lead 55, whereas the remaining sides of said elements are connected with switch contacts 53 of the previously referred to selector switch 36. v

A wiring diagram of the meter II is shown in Figure 4, and which diagram shows the meter to be a contact making meter such as may be bought on the open market with a complex movable element having four parts which are coupled together mechanically and move as a unit. These four parts are: an indicating pointer I4, an operating or deflecting coil 54, a holding coil 55, and a movable contact 56. The movable contact 55 is arranged to make contact with the adjustable pointer contact I3. The electrical terminal to the adjustable pointer contact I3 is labelled with letter A, and the electrical terminals to the operating coil 54 are identified by letters B and C. The operating coil 54 and the holding coil 55 are connected together at a common point, indicated by letter C, which is con-- nected to output terminal 38 of the bridge.

An interrupting circuit 66 is connected between the first tworesistors 43 and 44 of the supply lead 40 by means of a lead BI and the remaining supply lead 4| by means of another lead 62 and to terminal A of meter II by lead 63. The

first referred to lead SI of the interrupting cir-- cuit 66 is divided and is connected with separate neon lamps I5 and I6, previously referred to, after passing through resistors 64 and 65, respectively. A condenser 66 is connected between the resistors 64 and 65 between the latter and the neon lamps I5 and I6. The lamps I5 and I6 are thence connected with the previously referred to leads 62 and 63 and with the supply lead II and the meter terminal A, as previously described. A control relay 6! is connected in the first referred to lead of the interrupting circuit and has for its purpose the regulation and control of a heat control valve or the like, not shown, such as those ordinarily used in smoke houses, ovens or the like. An audio alarm, not shown, may also be included in connection with the relay 67. 1

In operation, the panel I2 is installed on the outside of a smokehouse, oven or other cooking compartment where the meter II and the neon lamps I5 and I6 will be visible to the operator. Inside of the smokehouse or the like, the probe or probes I I, as the case may be, are inserted in the meat to be cooked with the'pointed probe tip I9 near the center thereof. The bridge is initially balanced by means of the adjustable potentiometer 34, and the variable resistor 46. The adjustable potentiometer 34 is used to adjust the minimum scale reading desired, and the variable resistor 46 is used to adjust the full scale reading. Preferably, the adjustments of the potentiometer 34 and the variable resistor 4 are made at the time of fabricating the described temperature indication apparatus and need not be adjusted thereafter. The adjustable contact point I3 may be manually adjusted by the operator to control the internal'temperature desired. When the movable contact56 contacts the adjustable contact I3 the cook-off point has been reached. The contact thus made energizes the relay 61 and the interrupting circuit 66, closing the heat control valve or the like on the smoke house." The operating coil 54 will operate as a normal indicating instrument, deflecting in proportion to the bridge output voltage across terminals B and C, and the movable pointer I4 will indicate the bridge output voltage on the scale- (not numbered) of the meter Since a DArsonval type meter movement, as in the present meter II, is not capable of exerting sufiicient mechanical force to maintain a stable electrical contact, and would tend to either stick or bounce; at the critical contact position, a holding coil 55 or the like is necessary to amplify the torque for maintaining contact. The instrument shown uses a holding coil type of torque amplifier comprised of the described coils 54 and 55 which are pivetally mounted, not shown, in the meter II. Inmakw ing contact, current fiows through leads 6I, relay 6?, resistor 64, neon lamp I5, terminal A, hold-1 ing coil 55 and through terminal C back to ter-' minal 35 and line 4|. The current flowing through holding coil 55 provides the additional torque referred to so as to maintain stable elec-' trical contact between contacts 56 and I3. This; additional torque normally tends to hold the electrical contacts and would not permit the contacts to open, although the operating coil current may drop to near zero, except for the action of the interrupter circuit 60. Before the con tact is made, all the current through the relay; 61 and interrupter circuit will flow through resistor 65 and neon lamp I6. The condenser- 66 does not allow current flow through the other; side of the interrupter circuit -or resistor; 64. With current flowing through lamp I6, the lamp will glow and will give a steady visual indicationto the operator that the temperature is below the critical or pre-set control temperature.- As the internal temperature in the meat increases and rises to thevalue permitting closing oi the movable contact 56 and the adjustablecontact I3, the neon lamp I5 will be provided with a ree, turn path to-line 4| whereby current may flow through resistors 64,- relay 67 andall resistorsin the return path, and at which time the charge, of the condenser 66 is reversed which momen tarily extinguishes the other lamp I5. When the condenser 66 has become polarized in the opposite direction,- thevoltage drop across neon lamp I6 vwill'have reached the ionizing potentialnecessary to cause the-lamp It to conduct. "The period of time involved by the transition of lamp I5 to lamp I6 is dependent on the product vof the sum of theresistors 54 and 55 and the con denser 66. It will be, noted when neon lamp I6 conducts, neon lamp I5 is extinguished momentarily due to the reversing offpolarity in :the; voltage across condenser 66, but, will conduct again at the end of the charge period. This interaction of lamps I5 and I6;will continue as long as the contacts 55 and I3 are closed, The:

contact I3 and the remaining resistors and provides a period in which no torque is applied to the contacts which will permit opening of the contacts 56 and is if the operating coil current has fallen below the value sufficient to maintain the contact position. While the neon lamp :5 is extinguished, the current through the holding coil 55 is zero and the meter contacts 58 and it are permitted. to open if the temperature value is such that the operating coil torque is below the critical value. With neon lamp It conducting, the current through neon lamp l6 combined with the charging current of condenser 56 and resistor 64 will be sufficient to maintain the relay 6'! in a closed position, thus preventing the smoke house from further heating. As the temperature, and thus the deflection oi the movable pointer M, are of high enough value to maintain the contacts 56 and [3 in a closed position during the no current period of holding coil 55, the relay 6'! will remain closed and the heating source will be removed allowing the temperatures to diminish. In order to maintain a steady temperature, it will be necessary to reestablish the heating source when the temperature has diminished by a small amount. Since the holding coil 55 and contacts 58 and I3 are being permitted to open periodically, the diminishing temperatures will cause the contacts to break and the lamp i5 will no longer conduct. Lamp It will remain conducting but will not have sumcient current to retain relay $1 in closed position, and at which time relay s! will be de-energized and the source of heat will be reestablished. As long as the contacts 5E and [3 are closed, the lamps l5 and I6 blink alternately and the relay 6! remains closed. The alternate blinking of the lamps l5 and it provide visual indication to the operator that the instrument has reached the critical control point and in the shut-oil state. An audio alarm, not shown, may be connected to the relay to give additional warning that the critical temperature has been reached.

The present invention is not limited to the construction herein shown and described but may be made in many ways within the scope of the appended claims.

What is claimed is:

1. Apparatus for indicating and controlling internal temperatures in food while processing the same, said apparatus comprising an electrical resistance bridge, one arm of which is in the form of a negative temperature co-ei ficient resistor element adapted to be inserted in the food to be cooked, a D. C. source of constant voltage connected with the in-put terminals of said bridge, a meter connected across the output terminals of said bridge, said meter including a movable pointer and contact mechanically coupled with each other for operation in unison, an adjustable contact pointer arranged for making contact with the last said contact, an operating coil and a holding coil connected in series with each other and carried by said movable pointer and connected at one end thereof with said contact carried by said movable pointer, an interrupting circuit comprising a pair of gas discharge tubes each having a resistor connected in series therewith, a relay for controlling a heat source connected with both of said resistors on the ends thereof opposite said gas discharge tubes, a condenser connected between the said lamps between the same and the said resistors, the end of said relay opposite said resistors being connected with said D. C. source and one of said gas discharge tubes also being connected on the side thereof opposite its respective said resistors with said D. C. source, the remaining said gas discharge tube being connected with said adjustable contact forming a part of said meter.

2. In apparatus for indicating and controlling internal temperatures in food while processing the same as defined in claim 1, a probe adapted to be inserted in said food and including said negative co-eflicient resistors therein and forming a part thereof, said probe comprised of a tube having a tapered point of heat controlling material on one end thereof and having said negative co-efficient resistor elements mounted in said tube and against the inner end of said tapered point, and spring means carried within said tube retaining said element in its described position.

3. In combination with a contact meter as described in claim 1, an interrupting circuit comprising a pair of gas discharge tubes each having a resistor connected in series therewith, a relay forming a part of said interrupting circuit and connected with both of said resistors on the ends thereof opposite said gas discharge tubes, the end of said relay opposite said resistors being connected with one side of a D. C. source and one of said neon tubes being connected on the side thereof opposite its respective resistor with the remaining side of said D. C. source, and means connecting the remaining said tube on the side thereof opposite its respective said resistor with said adjustable contact in said meter.

RAYMOND B. BASHAM.

No references cited. 

